In this component of the Program Project we propose to extend gene regulatory network (GRN) analysis to the whole of the sea urchin embryo from early cleavage to shortly before feeding begins. Specific perturbations of gene expression are known which knock out development of specific parts of the embryo, and it is proposed to use these to isolate sets of regulatory and other genes by high sensitivity differential array screening that are specifically required for: skeletogenesis; specification and differentiation of aboral ectoderm; specification and differentiation of the oral ectoderm, ciliated band and hood; specification and differentiation of the archenteron, hindgut and foregut/midgut. Spatial and temporal expression of cDNA clones thus isolated will be characterized. GRNs for these components of the embryo will be formulated on the basis of a large-scale perturbation analysis including all relevant genes, and the components of the GRNs will be interlinked by examination of the regulatory targets of the signaling interactions by which the domains of the embryo are functionally coordinated during development. Key nodes of the GRNs will be subjected to experimental challenge by cis-regulatory analysis. The Proposal also includes development of various specific new technologies, some by a collaborative effort with our partners in the Program Project.